Chemistry KS2

*CONFIDENTIAL 2
CLASS:………………
NAME: …………………………………………….

KOLEJ TINGKATAN ENAM SHAH ALAM
JALAN TIMUN 24/1

SHAH ALAM, SELANGOR DARUL EHSAN

PENTAKSIRAN SEMESTER 2 STPM 2021 KALI KEDUA

CHEMISTRY 962/2

PAPER 2

DURATION: 1 HOUR 30 MINUTES

Instruction to candidates
DO NOT OPEN THIS QUESTION PAPER UNTIL YOU ARE TOLD TO DO SO

Write your name, I.C number and class in the space provided. There For examiner’s use
are fifteen questions in Section A. For each question, four choices of
answers are given. Choose one correct answer and indicate it on the Section A
multiple-choice answer sheet provided. Answer all questions. 1-15

Answer all the questions in Section B. Write your answers in the Section B
spaces provided. 16

Answer two out of the 3 questions in Section C. Write your answer on 17
your examination test pad. Begin each answer on a new sheet of
paper and arrange your answers in numerical order. Section C

This question paper consists of pages TOTAL

Prepared by: Checked by: Validated by
……………………………
……………………..…. …………………………… Pn Maziah Binti Muhammad Zain
Mas Liana Binti Mansor Pn Marini Binti Abdul Ghani
Head of Department
Head of Chemistry Unit

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Section A [15 marks]

Answer all questions in this section.

1. The table shows the enthalpy change of neutralisation per mole of water formed, ΔH, for
various acids and bases.

acid base ΔH / kJ mol–1
hydrochloric acid sodium hydroxide –57.0
sodium hydroxide –54.0
P –52.0
hydrochloric acid Q –57.0
R
nitric acid

What are P, Q and R? Q R
ammonia potassium hydroxide
P sodium hydroxide
A. ethanoic acid ammonia ammonia
B. ethanoic acid sodium hydroxide potassium hydroxide
C. sulphuric acid
D. sulphuric acid ammonia

2. Sodium ions can be formed from sodium atoms.
Na (s) → Na+ (aq)

Which quantities are not required to calculate the enthalpy change of formation of gaseous
sodium ions?

A. enthalpy change of atomisation of sodium
B. first ionisation energy of sodium
C. enthalpy change of formation of sodium
D. enthalpy change of hydration of sodium ion

3. The standard enthalpy changes of formation for iron (III) oxide and carbon monoxide are

A -822 kJ mol-1 and -110 kJ mol-1. What is the standard enthalpy change for the following
C
reaction?

Fe2O3 (s) + 3 C (s) → 2 Fe (s) + 3 CO (g)

- 932 kJ mol-1 B - 712 kJ mol-1
- 492 kJ mol-1 D + 492 kJ mol-1

4. When dilute acid is added to an aqueous solution containing nitrite ions, gases are evolved.
2 H+ (aq) + 2 NO2- (aq) → H2O (l) + NO (g) + NO2 (g)

Which statements correctly describe the process?

I. The NO2 (aq) ion undergoes disproportionation.
II. The H+ (aq) ion is oxidised by NO2- (aq).
III. The H+ (aq) ion act as the acidic medium of the reaction
IV. This reaction is not a redox reaction

A. I and II only B. II and III only
C. I and III only D. II and IV only

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5. When 193 C of electricity are passed through a molten compound of a metal, 1.00 x 10-3 mol of

atoms of the metal is deposited at the cathode. What could the metal be?
[Faraday’s constant = 96500 C mol-1]

I. copper II. lead III. silver IV. sodium

A. I and II only B. II and III only
C. I and III only D. III and IV only

6. In the commercial electrolysis of brine, the products are chloride, hydrogen and sodium
hydroxide. What is the maximum yield of each of these products when 58.5 kg of sodium
chloride is electrolysed as brine?

Cl2 H2 NaOH
A 35.5 kg 1kg 40kg
B 35.5 kg 2kg 40kg
C 71 kg 1kg 40kg
D 71 kg 1kg 80kg

7. The graph below shows the variation of two physical properties of elements in Period 3 of the
Periodic Table

XX

Na Ar Na Ar
What are the physical properties that the graphs refer to?

X Y
A. Melting point Ionisation energy
B. Electrical conductivity Melting point
C. Ionisation energy Atomic radius
D. Electrical conductivity Atomic radius

8. The elements radon (Rn), francium (Fr) and radium (Ra) have consecutive proton numbers in
the Periodic Table. What is the order of their first ionisation energies?

Least endothermic Most endothermic
Rn
A Fr Ra Ra
Rn
B Fr Rn Fr

C Ra Fr

D Rn Ra

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9. Which of the following elements is in Group 2 of the Periodic Table?

Element Melting point / 0C Density / g cm-3 Electrical conductivity / -1 m-1
A. 98 0.97 2.7 x 107
B. 113 4.93 8.2 x 10-8
C. 649 1.86 5.4 x 106
D. 1744 10.4 4.8 x 109

10. Which of the following statements is true for strontium or its compounds?

A. Strontium hydroxide is dehydrated to the oxide on being heated.
B. Strontium does not react with steam.
C. Strontium carbonate decomposes at a lower temperature than calcium carbonate.
D. Strontium does not burn in air.

11. The following diagrams show the structures of an element, X, its principal oxide, XO2 and its
halide, XCl4.

Element X Oxide of X, XO2 Halide of X, XCl4

What could the element be?

A. aluminium B. carbon C. lead D. silicon

12. Which one of the following properties would lead(IV) chloride be expected to possess?

A. high melting point B. ionic bonding
C. stable to hydrolysis in water D. tetrahedral molecule

13. Which of the following are disproportionation reaction?

I. 3 NaOCl → NaClO3 + 2 NaCl
II. Cl2 + 2 NaOH → NaOCl + NaCl + H2O
III. 3 Cl2 + 6 NaOH → NaClO3 + 5 NaCl + 3 H2O
IV. 4 HCl + MnO2 → Cl2 + MnCl2 + 2 H2O

A. I, II and III only B. I, II and IV only
C. I, III and IV only D. II, III and IV only

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14. A new element "Ovultine" is found and is placed in the lowest position in Group 17 of
Periodic Table. What are expected properties of astatine at 25oC?

Colour Physical state Oxidising power
A. Black Solid Weak
B. Black Solid Strong
C. Violet Solid Strong
D. Violet Liquid Weak

15. When sodium salt, NaX is warmed with concentrated H2SO4, white fumes evolves. What
could be observed if a few drops of aqueous AgNO3 are added to aqueous solution of NaX?

A. A white precipitate is formed. B. A yellow precipitate is formed

C. A colourless solution is formed. D. A cream coloured precipitate is formed

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Section B [15 marks]
Answer all questions in this section

16. (a) Samples of calcium and strontium are placed separately in water at room temperature and left
for one day . In each case, describe what you would see and write a balanced equation for
each reaction.

Elements Observations Equations

i. calcium ...................................................................................
...................................................................................
...................................................................................

ii. strontium ...................................................................................
...................................................................................
...................................................................................

[4 marks]

(b) Strontium nitrate, Sr(NO3)2 undergoes thermal decomposition.

i. Write a balanced equation for this reaction. [1 mark]

………………………………………………………………………………………………...

ii. Explain why a high temperature is required to decompose strontium nitrate. [2 mark]
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17 (a) Silicon dioxide is the main component used to make glass. Among the most common and
cheapest glass produced is soda glass which is manufactured by mixing silicon dioxide,
sodium carbonate and limestone.

i. State one of the component in soda glass, and write the equation for the formation of the

component stated. [2 marks]

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ii. State the compound added to silicon dioxide to form borosilicate glass and state one of its

property and its application. [3 marks]

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(b) Silicones are rubber-like materials used commercially in a wide variety of products.
Commercial silicones have infinite O-Si-O chains with alkyl or aryl groups attached to the
silicon atoms.

i. Draw the structure of chain silicone showing three repeating units with alkyl groups.
[2 marks]

ii. State one property of silicone. [1 mark]

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Section C [30 marks]
Answer any two of the three questions below

18. The reaction between ethane, C2H6 and chlorine gas, Cl2 to form chloroethane, C2H5Cl and
hydrogen chloride, HCl, can be described in the equation below

C2H6 (g) + Cl2 (g) → C2H5Cl (g) + HCl (g)

(a) Given then enthalpy of atomisation for these compounds are

Species Enthalpy change
Ethane, C2H6 of atomisation
Chlorine, Cl
+ 405 kJ

+ 121 kJ

Chloroethane, C2H5Cl + 418 kJ
Hydrogen chloride, HCl + 184 kJ

i. Define enthalpy change of atomisation. [1 mark]

ii. Calculate the enthalpy change of reaction for the reaction between ethane and chlorine.
[6 marks]

iii. Draw the energy level diagram for the reaction [3 marks]

(b) The enthalpy of solution of lead (II) chloride and sodium chloride are + 95 kJ mol-1 and

+7.0 kJ mol-1 respectively. Explain the difference between the solubilities of lead (II)

chloride and sodium chloride in terms of bonding. [5 marks]

19 (a) An alkaline fuel cell, as shown in diagram below, is used by astronaut as one of the energy
and electrical sources in outer space.

i. Write the reaction equation at cathode, anode and overall equation for the fuel cell above.
[3 marks]

ii. Calculate the voltage for the alkaline fuel cell above. [2 marks]

iii. A fuel cell can also works under acidic condition to produce the same voltage under

standard condition. Explain the statement above [2 marks]

iv. State two advantages of fuel cell compare to other chemical cell. [2 marks]

(b) Using suitable standard reduction potentials, describe the chemistry involved in the rusting

of iron under acidic environment [6 marks]

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20 (a) Describe the reactions that occur when chlorine is bubbled through cold and hot, aqueous sodium
hydroxide. Write equations and explain how the oxidation number of chlorine changes during
these reactions. What observation would make it clear that the chlorine had reacted? [6
marks]

(b) Table below list the melting points and boiling points of chlorine, bromine and iodine.

Elements Melting point / oC Boiling point / oC
Chlorine - 101 - 34.6
Bromine - 7.2 58.8
Iodine 114 183

Discuss the trend with regard to the structure and bonding of these elements [3 marks]

(c) Chlorine is often used as disinfectant and bleaching agent in swimming pool. Explain the role

of chlorine as bleaching agent in swimming pool, and the effect of exposing the mixture

under sunlight, hence write suitable equations involved. [6 marks]

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